1. Technical Field
The present invention generally relates to portable computers. More specifically, the present invention relates to a keyboard illumination device for portable computers, including notebook portable computers that are convertible (switchable) to tablet computers.
2. Related Art
Notebook portable computers (hereinafter referred to as “notebook PCs”), which are becoming widespread today, have a mechanism that allows the notebook PCs themselves to illuminate the keyboards in order to allow the notebook PCs to be used without inconvenience even in environments where sufficiently bright illumination cannot always be obtained (e.g., when the user uses the notebook PC for work during in-flight sleep time while ensuring that it does not cause inconvenience to people around him or her.)
FIG. 1 shows a mechanism of a typical notebook PC. That is, a notebook PC 100 has a cover unit (a cover) 120 including a display screen 110, such as an LCD (liquid crystal display) device. Typically, the cover unit 120 has a structure in which the peripheral edge portion (in particular, the upper edge portion in the vicinity of the upper edge of the display screen) protrudes in the shape of a projection toward the front side of the display screen so that, when the cover unit is closed, a main unit (a main-body unit) 130 including a keyboard comes into close contact with the cover unit in such a manner that no gap appears therebetween. With this arrangement, a light source 140, such as an LED (light-emitting diode), is installed in an embedded manner in the projected portion in the vicinity of the center of the upper edge portion of the cover unit, so that light can be emitted downward to the keyboard, thereby making it possible to illuminate the keyboard and so on.
Today, while serving as notebook PCs, portable computers that can also serve as so-called “tablet portable computers” (hereinafter referred to as “tablet PCs”) have become available (such dual-purpose portable computers will hereinafter be referred to as “convertible PCs”). A tablet PC has a display screen with a touch input system and allows inputting to the display screen in a tablet (a writing board or flat board) manner by using a finger or pen (stylus).
In the convertible PC that can be used as a notebook PC and a tablet PC, when the cover unit including the display screen is open, rotating the cover unit by 180° about a vertical axis passing through the display screen of the cover unit, i.e., switching the obverse surface (the side where the display screen is provided) and the reverse surface (the side where there is no display screen), and closing the cover unit again allows the cover unit to be overlaid on the upper surface (the surface having a keyboard and so on) of the main-body unit with the display screen side facing upward. This allows the PC to be used as a tablet PC in which the display screen is used as a handwriting input section. A main feature of mechanisms of the convertible PC is that, when the convertible PC is used in a tablet PC mode as described above, a center latch mechanism (a latch) provided at the center of the upper edge portion of the cover unit latches (secures) the cover unit and the main-body unit in order to prevent the cover unit from being easily opened.
When the convertible PC having such a mechanical feature is used in the tablet PC mode, the surface of the side having the display screen, such as an LCD, needs to be flat for use as a handwriting input section. Consequently, a projected portion provided in a typical notebook PC, which protrudes toward the front side of the display screen, cannot be provided on the cover unit. Thus, a PC having such a mechanism cannot employ a conventional mechanism and method for illuminating the keyboard surface by embedding a light source, such as an LED, for illuminating a keyboard in the projected portion of the cover unit and emitting light toward the lower edge of the cover unit, unless it is modified.
Some references are available regarding known technologies for illuminating a PC, including a keyboard, without providing a projected portion on a cover unit including the display screen of a notebook PC or the like or without providing a light source at a projected portion on the cover unit.
A technology disclosed in Japanese Unexamined Patent Application Publication No. 4-333023 is directed to a device and so on for a PC including a display device utilizing external light, such as a reflective LCD. When it cannot be expected to obtain sufficiently bright external light for illuminating the display screen of the PC, the disclosed device causes a point light source for illuminating the display screen, such as a reflective LCD, to protrude from the cover unit to a position where the display screen can be illuminated. However, because the device is intended to directly illuminate the display screen, the point light source must be made to protrude to a considerable degree from the cover unit including the display screen. This requires extra cost for providing a mechanism for making the point light source protrude. This configuration is also unsuitable as a mechanism to be employed for the convertible PC, since the surface at the display screen side cannot be made flat during use.
A technology disclosed in Japanese Unexamined Patent Application Publication No. 8-76882 is directed to a device for illuminating a keyboard and so on by utilizing light emitted from a fluorescent lamp for backlight which is built into a cover unit including a display screen. Light emitted from the fluorescent lamp is reflected by a reflector disposed on the upper edge portion of the cover unit, and the reflected light is focused on the keyboard by a condenser lens disposed below the reflector. However, since the light source of the device is a fluorescent lamp (e.g., a cathode tube) for backlight and not a point light source, the reflector and the condenser lens also need to have the same length as the longitudinal dimension of the fluorescent lamp. This leads to a large-scale device that requires extra cost. Although the light source is disposed inside the cover unit, the condenser lens and so on must be provided at a position that protrudes from the cover unit in order to illuminate the keyboard. Consequently, this configuration cannot also be employed as a mechanism for the convertible PC, as in the previous example.